bought a used 2011 HHR, 36108 miles, check engine light on. Took it to Chevy dealer, diagnostic cost me $90, it needed a vent valve that cost $29. Not sure of what the code was

 

Welcome to the site. I doubt that there's any similarity between your problem and the one that's the topic of this thread. But since yours was solved by replacing the vent valve why wouldn't have been covered by the 8 year/80,000 mile emission systems warranty? Shouldn't a 2011 have a 100000 mile warranty anyway? I'd ask the dealer those questions if it were me.....

 

Only had a 3 yr/36,000 mile mfgr warranty and since I was over the warranty pro-rates the repair. They don't pay for the diagnostic, only the part and they gave me $100 deductible toward repair. I have a 100000 mile on the powertrain, nothing else